The present invention relates to a self-latching device for fastening a hinged closure member, in particular a door or a gate, which device comprises a frame arranged to be mounted on the hinged closure member, a latch bolt mounted on said frame so as to be movable in a predetermined direction between a latching position and a retracted position, the latch bolt being a self-latching bolt arranged to be moved towards its retracted position by contact with a striker element when closing the closure member, a latch bolt spring arranged to bias the latch bolt into the latching position, and operator means mounted on top of the frame so as to be operable from both sides of the closure member and connected by means of a latch bolt operating mechanism to the latch bolt for moving it from the latching to the retracted position.
The self-latching device can be mounted on various types of doors, gates, etc. However, the latching device according to the present invention is especially suited for being mounted in an upright position on top of a gate in a safety fence for preventing small children from entering a certain dangerous area, such as a swimming pool area.
In several countries there are legal regulations for swimming pool gates. Most of these regulations specify for example a minimum height for the safety gates. An important characteristic is also the vertical distance between two potential supports allowing children to climb over the gate, for example between the lowermost horizontal tubular member of a gate and the door handles when these protrude on the back and on the front of the gate. The distance between two potential supports must also be greater than a minimum distance. By mounting the latching device in an upright position on top of the gate with the operator means on the upper side of the latching device, the height of the gate may therefore be limited. According to some regulations, the operator means of the latching device must be situated at a height higher than the minimum height of the gate itself. Also in this case the height of the gate can be limited due to the fact that the latching device can be mounted on top of for example a tubular member projecting above the actual gate itself.
U.S. Pat. No. 3,282,617 discloses a self-latching device comprising a spring-biased latch bolt protruding out of the bottom of a vertical tubular member of the gate. This latch bolt co-operates with a striker plate fixed to a fence post below the latch bolt. On the upper end of the tubular member of the gate a cap is fitted so that it can be manually lifted axially of the tubular member. A cable extending through the tubular member connects the cap with the latch bolt to enable to withdraw the latch bolt out of the striker plate by lifting the cap. The cap is placed at such a height on the gate that it is out of the reach of small children.
A drawback of this known self-latching device is that the gate has to be of a quite rigid construction since it is fastened at its lower edge to the striker plate so that considerable torsion stresses may be generated in the gate when somebody pulls or pushes to the upper edge of the gate. A further drawback is that the striker plate forms a projection at a certain height on the fence post against which a person passing the gate may hurt himself by knocking with his legs or feed against the striker plate. Moreover, the cavity in the striker plate can easily become filled with dirt. An important drawback is further that the co-operation between the latch bolt and the striker plate requires a quite accurate positioning of both elements with respect to one another. Each time the gate sags somewhat the height of the striker plate has thus to be adjusted to ensure a reliable functioning of the self-latching device.
WO-A-92/03631 discloses a self-latching device for hinged swimming pool gates comprising also a bolt protruding out of the bottom of the latching device into a retaining element. This retaining element comprises a permanent magnet to draw the bolt into the retaining element against the bias of a compression spring. The latching device can be mounted on top of the gate so that the bolt is situated at a certain height on the gate and so that the torsion stresses in the gate are thus reduced. In practice, the latching devices disclosed in WO-A-92/03631 are mounted on the fence post so that the retaining element protrudes from the gate instead of from the fence post. A drawback of such an arrangement is however that a person who wants to open the gate has to have both hands free as he has to pull the bolt of the latching device with one of his hands upward and at the same time he has to open the gate with his other hand. A further drawback of this known latching device is that the retaining element has to be positioned perfectly underneath the bolt in order to be able to draw the bolt by magnetic attraction into the retaining element. Consequently, when the gate sags or otherwise moves somewhat, the distance between the permanent magnet and the bolt will become immediately so great that the magnetic force will no longer be able to attract the bolt against the tension of the compression spring and the gate will thus no longer be latched. A regular check up and adjustment of the mutual position of the retaining element and of the latching device will thus be necessary.